ubfractions of Coxiella burnetii, the etiologic agent of Q ever, which confer immunological efficacy as measured by umoral and cellular mechanisms have been investigated. ttempts to demonstrate the chemical nature of the reactogenic omponents of C. burnetii suggest that carbohydrate and lipid re involved in the Q-complex which induces mitogenic yporesponsiveness and negative modulation of cellular mmunologic functions. Using inbred strains of mice a model or the study of resistance to infection and reactogenic ctivities of candidate vaccines has been established. ctivation of murine peritoneal macrophages to perform on-specific tumoricidal cell cytotoxicity was assayed using hase I C. burnetii whole cell (WC) and chloroform-methanol esidue (CMR) vaccines. Macrophages from mice resistant, ntermediately sensitive and sensitive to C. burnetii infection ere activated by WC vaccine, whereas CMR vaccine was less ffective as a non-specific activator of macrophages. Murine onoclonal antibodies against phase I C. burnetii ipopolysaccaride (LPS) were produced. Iodination of phase I nd phase II WCs revealed a major outer membrane protein of bout 29.5K. This surface exposed protein was extracted in an queous buffered detergent system, purified to homogeniety by olumn chromatography and preparative sodium dodecyl sulfate olyacrylamide gel electrophoresis and determined to be an mmunodominant antigen using immunoblotting, enzyme-linked mmunosorbent assay and radioimmune precipitation. A phase 2 linical trial using phase I WC vaccine was initiated and hould be completed within a few months so that a phase 3 linical trial can be initiated and should be completed within few months so that a phase 3 clinical trial can be initiated n early 1985. Currently, the detoxified CMR derived from hase I WC is being produced so that phase I testing of this andidate Q fever vaccine can be initiated.